Electrical condenser



May 15, 1951 s. H. STUPA'KOFF" ELECTRICAL CONII'JENSER Filed Aug. '23, 1944 I I V INVENT I Semcm If Stupakafi Patented May 15, 1951 UNITED STATES PATENT OFFKCE ELECTEECAL CONDENSER Application August 23, 1944:, Serial No. 550,715

(Cl. 175-- l1) 1 Claim. 1

Ihis invention pertains to electrical condensers and their manufacture, and is for an improved condenser construction and a novel method of making the same. The invention is particularly applicable for use in small high-capacity condensers which have to have a high degree of accuracy under widely varying climatic and atmospheric conditions. While the invention is not limited to small condensers, it is particularly applicable to condensers which are required to be used in a restricted space, and which therefore have to be physically small.

At the present time, high capacity condensers are widely required in the field of radio and like equipment. Dirliculty has heretofore been encountered in making the condensers sufficiently compact, and at the same time immune to atmospheric conditions or chan es in atmospheric conditions.

According to the present invention, the electrical elements of the condenser are received within and held together by glass or glass and ceramic material, the glass being fused to the metal parts to form a hermetic seal, the glass or glass and ceramic serving to hold the parts together and in proper relation, and also providing a moisture-proof enclosure. The glass and the metal parts which it contacts may have their coefficients of thermal expansion matched, or so nearly matched that changes in temperature, brought about either by the sealing of the condenser in its manufacture, or by subsequent changes of temperature encountered in use, will not cause the glass to break or crack.

My invention may be more fully understood by reference to the accompanying drawings, in which:

Fig. 1 illustrates a longitudinal section through a condenser embodying my invention;

Fig. 2 is a View similar U Fig. l of a slightly modified form, wherein a combination of ceramic and glass is used;

Fig. 3 is a view similar to Fig. a further slightly modified form;

Fig. 4 is a view similar to Fig. 1, showing a multiplate condenser constructed in accordance with this invention; and

Fig. 5 is a view of? modification which is preferably used in high grade constructions, the view showing a side elevation, but not detached from the several parts constituting the condenser.

Referring first to Fig. l, the condenser therein illustrated may be many times the actual size of the completed condenser. The condensers,

.L showing still for example, may be small enough so that several of them may be placed on the base of a radio tube, one on each of the contact pins or the tube. As above indicated, however, the invention while primarily applicable to small structures is not limited as to The condenser as disclosed in Fig. 1 comprises two metal discs or plates which may be either circular, rectanguar, or any other convenient shape, these being designated 2 and 3 respectively. The plate 2 has a threaded outwardly extending projection 2a and the plate 3 has a similar projection 3a In the drawing, 2a is illustrated as being threaded, and 3a. is designated as smooth, but this is merely a matter of choice, and both may be threaded or smooth, depending upon whether the projections are to be soldered into the circuit or whether terminals utilizing nuts are to be employed. Each of the plates has a flat inner face. Sandwiched between the two faces of the discs, and of coextensive area therewith, a body of dielectric material. Preferably the dielectric material is formed of titanium dioxide or like ceramic having an inherent high dielectric property. The parts are held together by a glass shell or sleeve which fits snugly or tightly about the some assembly, and the glass is of a character which wets the metal bodies 2 and 3 and will seal itself thereto. Typically the metal elements 2 and 3 may be of a metal such as that sold under the trade-mark Kovar, and the glass is one of several wellkuown bore-silicate glasses, the coefficient of expansion of which is matched or substantially matched to that of the Kovar. The Kovar etal has a property that glass will Wet or adhere to the surface thereof when the glass is fused in contact withit.

The assembly is made either by fusing glass about the assembly or by fitting a preformed sleeve about the assembly and then heating it to a fusing temperature. In either event the glass seals to the metal elements 2, forming a, hermetic closure about the dielectric substance 5. It serves not only as a hermetic seal, but as a means for holding the parts firmly and fixedly together in a permanent assembly.

In the modification shown in Fig. 2, the construction is substantially the same as that shown in Fig. 1, except that the parts are fitted within a ceramic sleeve and the bore-silicate glass is applied at each end or the sleeve and over the surface of the sleeve to render it imperivous to air. In Fig. 2 the two plate elements are designated 3 and ll. Each is shown as having an outwardly extending stem portion 3a and 9a respectively, and these may or may not be threaded as indicated in Fig. l. Sandwiched between the two conducting plates 8 and e is a disc of high dielectric material is, this preferably being, as heretofore indicated, a titanium dioxide body. The disc is coextensive with the area of the plates 8 and Fitted about the periphery of the assembled structure comprising the members 8 and 9 and the intervening disc it is a refractory ceramic ring ii. A coating of glass I2 is over this ceramic ring and is fused to the metal 3 at each end of the ring. Here again the coefiicient of thermal expansion of the glass is preferably the same as that of the metal, or sufficiently closely matched so that the glass may be fused to the metal and will not break upon cooling, and will subsequently withstand br akage under any changes of temperature to which the condenser is normally subject.

In Figs. 1 and 2 the plates are illustrated as having integral stems. In Fig. 3 the plates of the condenser, designated l5 and it, are thin sheet metal. Connectors its and its respectively are soldered or otherwise secured to the sheet metal plates, the solder or other connecting material being designated l'l. interposed between the plates is a body of dielectric material It. A bead it of bore-silicate glass, or other glass that will wet the metal plates l5 and i6 and adhere thereto, and which preferably has its coefiicient of expansion properly adjusted to match that of the metal and I5, surrounds the periphery of the assembly and connects the two plates permanently together, excluding at the same time, atmospheric moisture. With this arrangement the connector pins !5a and l 6a do not have to be of the same metal as the plates l5 and i6.

Referring to Fig. 4, the structure is the same as that previously described, except that the con denser is a multiplate condenser. There are two end plates 29 and 21. Each of these plates is provided with a connector portion or stem Na and 25a, respectively. The plate is provided with a conductor strip Zllb which in turn supports the plates 2130. Likewise the plate 2| has a conductor strip 2th to which are connected plates Me. The plates 20c and 250 are alternately arranged and sandwiched between each two conducting plates as a layer or disc of insulating material, preferably of the type herein above described. Surrounding the assembly is a glass sleeve 22 which is fused at 23 to the plates 20 and 2!. The coefficients of thermal expansion of the plates 2% and 2| and the coefficient of expansion of the glass at 23 is preferably matched or closely matched so that the glass can be fused to the assembly to maize a fixed hermetically sealed condenser.

In the foregoing embodiments of the invention, the metal elements are indicated as themselves constituting the plate surfaces of the condenser. This type of construction may not give as high uniformity of results as may be desired. Different condensers made at the same time and by the same process might, if close tolerances were imposed, vary beyond a permissive range. Where a high degree of uniformity is desired, the dielectric body 25 may be metallized on each surface as indicated at 26 and 21. This metallizing may be done by depositing a film of metal directly on the dielectric body. The most convenient manner accomplishing this is to paint the surfaces of the ceramic body 25 with a paint that will form a continuous metal film. Silver paint may be used, but preferably a metal having a higher melting point, such for example, as platinum paint. The metal plates, formed of Kovar or other appropriate metal, and designated 28 and 29, may be coated with solder. The two metal elements and the metallized ceramic body are then pressed together and heated so that the plates 28 will be soldered to the metal surfaces 26 and 2?. The metal surfaces 26 and 21 will constitute the actual plates of the condenser. There will be no possibility of an intervening complete or partial film of air between the metal and the ceramic. Because of the absence of air or other substances between the metalized sur faces and the dielectric material, the full benefit of the high dielectric ceramic body is obtained and the condenser has a high capacity and low loss factor as well as improved uniformity.

After the soldering operation has been completed, a glass bead, such as shown in Fig. 1 or 3, is formed around the periphery of the assembly to hermetically encase the ceramic dielectric body 25 and firmly unite the two metal plates 28 and 255. In a construction such as this, the metal plates 23 and 29 serve to make contact with the metal films 28 and 27, and the metal films 2S and El are the actual charge carrying plates of the condenser. The metallizing of the ceramic may also be accomplished in other ways, as by spraying the metal onto the ceramic, and thereafter smoothing it off if necessary.

The invention provides an extremely compact, sturdy, and economical condenser which is hermetically sealed against atmospheric conditions. The condenser and the method of making it is further unique in that the material that forms the hermetic seal is formed or placed directly about and in contact with the dielectric material and is fused to the condenser plates themselves, avoiding the necessity of embedding the condenser in wax or other embedding material. The term glass is used herein in a general sense to include any glass like ceramic compound which may be caused to fuse and adhere to the metal plates at temperatures below that at which the metal plates will be detrimentally effected.

While I have shown and described certain speciflc embodiments of my invention, it will be understood that this is by way of illustration and that various changes and modifications are contemplated and are within the scope of the appended claim.

I claim:

A hermetically sealed condenser comprising a high capacity condenser assembly of a pair of spaced terminal conductor elements respectively including parts in conducting relation therewith and providing opposed charge-collecting areas, and a solid ceramic body of high dielectric material completely filling the space between said collecting areas and in intimate contact therewith, and an envelope of glass embracing the assembly and having portions at its ends respectively fused to one of said conductor elements, said glass envelope and conductor elements cooperating to form a hermetic enclosure for said dielectric body and respectively having thermal coefficients of expansion which are substantially matched.

SEMON H. STUPAKOFF.

(References on following page) 5 REFERENCES CITED Number The following references are of record in the 2163407 file of this patent: UNITED STATES PATENTS 2328352 Number Name Date 2,238,031 887,598 Delloye May 12, 1908 2,251,540 1,407,061 Gray Feb. 21, 1922 2,315,199 1,479,315 Pickard Jan. 1, 1924 2,370,082 1,591,177 Minge July 6, 1926 0 2,436,208 1,717,154 Hoover June 11, 1929 2,148,607 De Lange Feb. 28, 1939 2,157,715 Meggenhofen May 9, 1939 Number 2,159,793 Grundmann May 23, 1939 601,961

Name Date Pulfrich June 20, 1939 Payne Oct. 24, 1939 Stack Oct. 24, 1939 Hopfield Jan. 14, 1941 Brennan Apr. 15, 1941 Bushbeck et a1 Aug. 5, 1941 Gonningen Mar. 30, 1943 Slepian Feb. 20, 1945 Dressel Feb. 17, 1948 FOREIGN PATENTS Country Date Germany Aug. 28, 1934 

